Violent storms are natural phenomena that often generate winds having the potential for destruction of property and life. This potential is evidenced upon review of the storm systems known as Hurricane Hugo and Hurricane Andrew that struck the eastern coast of the United States. Hurricane Andrew was especially destructive taxing the entire nation in the form of rebuilding costs and insurance rates. In light of the escalating costs for rebuilding, home owners, business owners and insurance companies alike have a common goal in protecting property. Proper shuttering of windows and doors, typically the weakest portion of a structure, has become a necessity if the structure's contents are to be protected.
The study of storms have determined that storm shutters must withstand more than just high winds. In reality the majority of the destruction is a direct result of impacts by debris carried by these high winds. In an effort to reduce the destructive effect of such windborne debris, changes to the building codes in areas frequently subjected to these type storm systems have been proposed, notably in South Florida. One change that appears imminent includes requiring that storm shutters withstand a large missile impact test. The SBCCI Standard for Windborne Debris Impact Tests (SSTD 11-93) is presently proposed for inclusion in the South Florida Building Code, namely the county of Dade and Broward. Testing is performed by projecting a large object, such as a length of 2.times.4 lumber, at a high velocity of 50 feet per second or higher, against the storm shutter being tested. This is intended to simulate the impact of windborne debris in a hurricane or similar storm. To successfully pass the test the portion of a structure to be protected, such as a glass window or door, must remain intact after the projectile has impacted the shutter.
Along with providing protection from such windborne debris, it has been found desirable for storm shutters to be constructed of translucent materials so as not to nullify the main purpose of transparent glass windows and doors. The transparent materials prevent claustrophobic tendencies of occupants secured within the structure yet permits law enforcement officials to inspect shuttered structures.
A number of U.S. Pat. Nos., notably numbers 4,685,261, 4,175,357, and 5,228,238, disclose various types of translucent storm shutter assemblies having a transparent panel constructed with flat plastic sheets such as polycarbonate and mounted in a frame of aluminum or steel. A problem with polycarbonate is its thermal coefficient of expansion which is significantly higher than aluminum or steel. The plastic sheet used in the '261 and '357 patents is firmly secured to a frame with little if any allowance for expansion and contraction relative to the frame. Such restriction can cause the shutter assembly to become damaged even without exposure to storms. The plastic sheet used in the '238 patent, on the other hand, is mounted to its frame so as to allow each sheet relative freedom to expand and contract. As taught by the '238 patent, this problem may be avoided by mounting each plastic sheet in a frame so that it is relatively unrestricted and free to change in size in response to temperature changes. In order to accomplish this, however, the '238 patent discloses a very elaborate and thus relatively expensive storm shutter assembly.
A common problem shared by transparent storm shutters of the prior art is that in order to successfully pass a missile impact test, like that previously described, each plastic sheet is relatively thick, typically on the order of 0.5 inches or more. Since impact resistant plastics such as polycarbonate are relatively expensive, the cost of manufacturing transparent storm shutters increases proportionately to the thickness of the material. Thicker plastic sheets also make each storm shutter heavier and more cumbersome to transport, store, install and remove. In addition, as the weight of the storm shutter increases, the anchoring mechanism used to secure the storm shutter to a structure must be able to bear the additional weight as well as withstand the storm.
Therefore, there is a need for a transparent storm shutter that is relatively inexpensive to manufacture, and is easy to install and remove, yet capable of withstanding direct impacts from windborne debris during a storm.